ISO 14229-2:2013 specifies data link independent requirements of session layer services.
ISO 14229-2:2013 specifies common session layer services to provide independence between unified diagnostic services (ISO 14229-1) and all transport protocols and network layer services (e.g. ISO 15765-2 DoCAN, ISO 10681-2 communication on FlexRay, ISO 13400 DoIP, ISO 14230-2 DoK-Line, etc.)
ISO 14229-2:2013 specifies a common service primitive interface between OSI layer 4 (Transport) and layer 5 (Session) via so-called service request/confirmation/indication primitives. This interface allows seamless implementation of ISO 14229-1 unified diagnostic services (UDS) with any communication protocol titled "DoXYZ / CoXYZ" like ISO 15765 DoCAN - diagnostic communication over Controller Area Network, ISO 13400 DoIP, ISO 10681 communication over FlexRay, ISO 14230 DoK-Line.
ISO 15031 (emissions-related OBD) and ISO 27145 (WWH-OBD) support the standardized service primitive interface.